1. Field of the Invention
The present invention relates to a toner for use in a developer for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing, etc., and to a developer including the toner, an image forming method, and an image forming apparatus using the developer. More particularly, the present invention relates to a toner for developing an electrostatic image for use in (full-color) copiers, (full-color) laser printers, (full-color) plain paper facsimiles, etc., using direct or indirect electrophotographic (multicolor) developing methods, and to a developer including the toner, an image forming method, and an image forming apparatus using the developer.
2. Discussion of the Background
As U.S. Pat. No. 2,297,691 discloses, electrophotographic image forming methods typically include serial processes of forming an electrostatic latent image on a photoreceptor (electrostatic latent image bearer), developing the electrostatic latent image with a developer to form a visual image (toner image), transferring the visual image onto a recording medium such as paper, and fixing the image thereon.
Recently, in terms of saving energy, technologies capable of fixing at low temperature and copying at high speed have been developed, e.g., toners including a resin or a wax having a low softening point and having good low-temperature fixability. However, a toner having good low-temperature fixability is thermally vulnerable and likely to be solidified with heat generated by apparatuses or when stored (so-called blocking phenomena). Moreover, the toner has neither sufficient heat-resistant storage stability nor a sufficient fixable temperature band.
In order to make a toner have low-temperature fixability, thermal properties of a resin included in the toner need controlling. Thus, e.g., Japanese Patent No. 4,347,174 and Japanese published unexamined application No. 2007-233169 disclose including a melting miscible material having a plasticizing effect and compatible with a resin such as a crystalline polyester to lower a glass transition temperature (Tg) of the resin.
Further, Japanese published unexamined application No. 2008-242473 discloses a method of making the shape of toner particles and the content rate of a fine powder have a specific relation so that the resultant toner has good low-temperature fixability and heat-resistant storage stability. However, when the Tg is too low, the heat-resistant storage stability deteriorates. When flow tester ½ temperature (T1/2) is too low, the temperature at which hot offset occurs is lowered.
Some image forming methods specifying the Tg or flow tester ½ temperature (T1/2) disclose that the resultant toner has both good low-temperature fixability and heat-resistant storage stability. However, although generally successful, even Japanese Patent No. 4,347,174, and Japanese published unexamined applications Nos. 2007-233169 and 2008-242473 do not suffice for a toner to have both low-temperature fixability and heat-resistant storage stability, and need further improvement in terms of saving energy.
For these reasons, a need exists for a toner capable of forming high-quality images, having good low-temperature fixability and heat-resistant storage stability.